Group III-Nitride semiconductor devices, which include Nitrogen (N) and one or more of Aluminum (Al), Gallium (Ga), and Indium (In), or other group III materials, have attracted extensive attention in semiconductor fabrication technologies in recent years. Because of the higher electron mobility of the group III-Nitride materials compared to silicon, a group III-Nitride semiconductor device may have faster operation speed and allow wider band gap than a silicon semiconductor device. However, the fast operation speed of the group III-Nitride semiconductor device leads to a great amount of heat generation, which is a critical factor that impacts the power performance, the efficiency performance, and the reliability performance of the group III-Nitride semiconductor device. Accordingly, it is desirable to fabricate the group III-Nitride semiconductor device in a configuration for better heat dissipation.
For a high-speed group III-Nitride semiconductor device, Silicon-Carbon (SiC) is widely used to form a substrate, through which the heat generated by the group III-Nitride semiconductor device dissipates. In some high-power applications, SiC may not have high enough thermal conductivity to meet the heat dissipation requirement. A conventional way to solve this issue is to etch the SiC substrate away from the group III-Nitride semiconductor device, and form a high thermal conductivity substrate where the SiC substrate is removed. Normally, an ex situ transition layer with a minimum thickness (greater than 30 nm) is needed between the etched group III-Nitride semiconductor device and the high thermal conductivity substrate to achieve reliable bonding. As such, the ex situ transition layer will create a thermal barrier between the etched group III-Nitride semiconductor device and the high thermal conductivity substrate. Further, a temporary handling wafer is also needed to hold the etched group III-Nitride semiconductor device while forming the high thermal conductivity substrate back to the etched group III-Nitride semiconductor device. In some applications, forming the high thermal conductivity substrate, like diamond deposition, requires a higher temperature than the temporary handling wafer may stand. Consequently, the group III-Nitride semiconductor device with high thermal conductivity substrate, like diamond, may suffer from poor manufacturability.
Accordingly, there remains a need for improved semiconductor device designs that utilize the advantages of group III-Nitride materials and accommodate the increased heat generation of high performance group III-Nitride semiconductor devices. In addition, there is also a need to enhance the thermal performance of the semiconductor devices without increasing the device size.